The code is designed for single digit contexts, i.e 1-9.
We've hit our first app that uses context 10, so update the logic.

Bug: b/184105957
Bug: angleproject:5807
Change-Id: Ice5facad8a86f009c0a85d184db4a20e48eff248
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2796402
Commit-Queue: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Tim Van Patten <timvp@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>